Lapping is a method of planarizing a surface of a work piece (e.g., a bar sliced from a wafer) to reduce its surface topography (e.g., roughness). Such surface topography is formed, for example, when a wafer (e.g., an AlTiC wafer) is sliced into bars with uneven or rough surfaces. The bars can be mounted and polished in one or more precision lapping (i.e., polishing) processes to achieve desirable surface planarization and surface smoothness.
In one example lapping process, an electronic lapping guide (ELG) is used to accurately control the planarization of a surface of a work piece. As used herein, the term “work piece” refers to a structure, such as a bar or chunk, including one or more individual electronic components, such as microelectronic components or features. ELG sensors are embedded in a work piece with a surface to be lapped, and the work piece is attached to a lapping carrier releasably attached to printed circuit board (PCB). Connection points on the PCB are releasably bonded, via a wire bonding process, to one or more electronic lapping guide (ELG) bonding pads on the work piece. While the work piece is lapped (e.g., polished), a controlled amount of current is flowed via the PCB and each of the ELG bonding pads from a lapping controller to measure, in-situ and real time, the resistance of each of one or more ELG sensors electrically coupled to the ELG bonding pads. The resistance of each ELG sensor increases as the thickness of the work piece proximal to each of the ELG sensors decreases. Consequently, the change in the thickness of the work piece can be measured and the measurement is used to actively control lapping parameters during the lapping process. For example, such work piece thickness measurements can be used to selectively control the rate at which material is removed at different positions on the work piece (e.g., by applying more or less pressure to different positions along a length of the work piece) during a lapping process.